<template>
    <div class="pagination">
        <button :disabled="pageNum==1" @click="$emit('getpageNum',pageNum-1)">上一页</button>
        <button v-show="startNumAndEndNum[0]>1" @click="$emit('getpageNum',1)" :class="{active:pageNum==1}">1</button>
        <button v-show="startNumAndEndNum[0]>2">···</button>

        <button v-for="(page,index) in startNumAndEndNum" :key="index" @click="$emit('getpageNum',page)" :class="{active:pageNum==page}">{{page}}</button>

        <button v-show="startNumAndEndNum[continues-1]<totalPage-1">···</button>
        <button v-show="startNumAndEndNum[continues-1]<totalPage" @click="$emit('getpageNum',totalPage)" :class="{active:pageNum==totalPage}">{{totalPage}}</button>
        <button :disabled="pageNum==totalPage" @click="$emit('getpageNum',pageNum+1)">下一页</button>

        <button style="margin-left: 30px">共 {{total}} 条</button>
    </div>
</template>

<script>
export default {
    name:'Paginition',
    props:['pageNum','pageSize','total','continues'],
    computed:{
        totalPage(){
            return Math.ceil(this.total/this.pageSize);
        },
        startNumAndEndNum(){
            const {pageNum,totalPage,continues} = this;
            let start = 0,end = 0;
            // 总页数<连续页码数
            if(totalPage < continues){
                start = 1;
                end = totalPage;
            }else{
                // 总页数>=连续页码数
                start = pageNum - parseInt(continues/2);
                end = pageNum + parseInt(continues/2);
                if(start<1){
                    start = 1;
                    end = continues;
                }
                if(end>totalPage){
                    end = totalPage;
                    start = totalPage-continues+1;
                }
            }
            let arr = [];
            for(let i=start;i<=end;i++){
                arr.push(i);
            }
            return arr;
        }
    }
}
</script>

<style lang="less" scoped>
.pagination {
    text-align: center;
    button {
        margin: 0 5px;
        background-color: #f4f4f5;
        color: #606266;
        outline: none;
        border-radius: 2px;
        padding: 0 4px;
        vertical-align: top;
        display: inline-block;
        font-size: 13px;
        min-width: 35.5px;
        height: 28px;
        line-height: 28px;
        cursor: pointer;
        box-sizing: border-box;
        text-align: center;
        border: 0;

        &[disabled] {
            color: #c0c4cc;
            cursor: not-allowed;
        }

        &.active {
            cursor: not-allowed;
            background-color: #409eff;
            color: #fff;
        }
    }
}
.active {
    background-color: skyblue;
}
</style>